Method for implementing distribution of link state information in an optical network

ABSTRACT

A method for implementing distribution of link state information in an optical network includes: determining information of each link protection attribute section included in a Traffic Engineering (TE) link; carrying the information of each link protection attribute section in a customized TLV, respectively; distributing the TLV in the optical network via Traffic Engineering Link State Advertisement (TE LSA). With this invention, all the link state information such as multiple kinds of protection types included in one TE link can be carried in the customized TLV to distribute. Therefore, in the implementation of this invention, one TE link corresponding to one optical fiber can be configured with multiple kinds of protection types.

FIELD OF THE INVENTION

The present invention relates to optical network communication,particularly to a method for implementing distribution of link stateinformation in an optical network.

BACKGROUND OF THE INVENTION

Open Shortest Path First (OSPF) protocol is a routing protocol that iscommonly used in intelligent optical networks. Each router which runsOSPF protocol distributes its local link state information throughoutthe Autonomous System by flooding, ultimately every participating OSPFrouter can obtain all the link state information of the whole AutonomousSystem's topology, and all the OSPF routers have the same link statedatabase.

The flooding of OSPF link information is implemented via various LinkState Advertisements (LSAs). The standard OSPF LSAs are: Router-LSAs,Network-LSAs, Area Border Router-Summary-LSAs, Autonomous SystemBoundary Router-Summary-LSAs, AS-external-LSAs, etc. In order to meetthe requirements of Traffic Engineering (TE), OSPF extension protocol isused to extend the standard LSA, i.e., by using Type 10 Opaque LSA forreleasing related link information, which is called Traffic EngineeringLink State Advertisement (TE LSA).

The TE LSA, which is an opaque LSA, has two kinds of top-level TLVs(Type/Length/Value): Router Address TLV and Link TLV. Wherein, the LinkTLV mainly describes the link properties of Traffic Engineering (TE) anddefines standard sub-TLVs numbered 1 to 16, i.e., secondary TLVs, whichinclude Link Type, Link ID, Local interface IP address, Unreservedbandwidth, Link Protection Type, Shared Risk Link Group, InterfaceSwitching Capability Descriptor, etc; wherein, the link protection typeis No. 14 sub-TLV.

According to IETF definition, the protection type of the links in anautomatic switching optical network includes Extra Traffic, Unprotected,Shared, Dedicated 1:1, Dedicated 1+1, Enhanced, etc. When an opticalfiber is configured with Multiplex Section Protection (MSP), protectiontypes of channels in the fiber can be categorized into three types:Enhanced, Unprotected and Extra Traffic; that is, protection types ofdifferent channels in an optical fiber can be different from each other,so it is inappropriate for a fiber link to define only one protectiontype.

Presently, when an optical interface is configured with MSP, the linksfor the bidirectional shared multiplex section can be divided into threeTE links of different attributes: enhanced TE link, extra traffic TElink and unprotected TE link. In this way, the protection types of allthe bandwidth resource for each TE link are identical. The three TElinks generate LSAs to be flooded respectively.

It can be seen from the above mentioned representations:

(1) when there is traffic on a link, a multiplex section can not bedynamically configured, modified or deleted in this link, becauseconfiguring, modifying or deleting the multiplex section can result inregeneration of the TE link index for the optical interface. Forexample, if no multiplex section is configured initially, there existsan unprotected TE link in the optical interface; when multiplex sectionsare configured, the original TE link is deleted and then three new TElinks are generated in accordance with the new configuration; in thisway, meaning of the link TE index for the current traffic stored insignaling has changed, which may likely cause that the index does notrelate to the original TE link.

(2) one optical fiber is represented by three TE links, resulting inlarge number of TE links and much flooded information, which increasesthe burden of network.

SUMMARY OF THE INVENTION

The present invention aims to provide a method for implementingdistribution of link state information in an optical network includingthe steps of:

determining information of each link protection attribute sectionincluded in a Traffic Engineering (TE) link;

carrying the information of each link protection attribute sectionincluded in the TE link in a customized Type Length Value (TLV),respectively;

distributing the TLV of Traffic Engineering link in the optical networkvia Traffic Engineering Link State Advertisement (TE LSA).

wherein, the step of determining information of each link protectionattribute section included in a TE link includes the steps of:

determining the number of link protection attribute section structuresfor the TE Link and information of each link protection attributesection carried in each link protection attribute section structure, inaccordance with the subscriber configuration on the link.

The information of each link protection attribute section includes:

protection type of the section and/or information of bandwidth resourceoccupied by the section.

The step of carrying the information of each link protection attributesection included in the TE link in a customized TLV respectivelyincludes the step of:

carrying the information of each link protection attribute section onthe TE link in a field of link protection attribute section structure ofthe customized TLV.

In an embodiment of the present invention, the customized TLV furtherincludes:

a field for the number of link protection attribute section structures,which is used to carry the number of the link protection attributesection structures divided from bandwidth resource in accordance withthe subscriber configuration on the link;

a field for the offset of link protection attribute section structures,which is used to carry an offset from the start of TLV structure to thelink protection attribute section information; wherein an offset pointerpoints to link protection attribute section structure sequence which isused to carry the information of each link protection attribute section.

The section protection types include:

Extra, Unprotected, Shared, Dedicated 1:1, Dedicated 1+1 and Enhanced.

The information for bandwidth resource occupied by the section includes:

the minimum bandwidth supported by the section and bandwidth resourceoccupied by the section.

It can be seen from the technical solution according to an aspect of thepresent invention that it effectively solves the problem of one TE linkconfigured with multiple kinds of protection types, and can be well usedin case that one TE link is configured with multiple kinds of protectiontypes, such as multiplex section, span protection, etc. The protectionattribute of TE link is transferred from link level to each protectionattribute section, and the protection attribute in the protectionattribute section structure and the information of section bandwidthresource are encapsulated into a customized TLV of TE link, and the TLVis flooded through No. 10 opaque LSA in the whole network, and thereforeone TE-link can provide bandwidth of multiple kinds of protectionability.

In addition, with the method for distributing link state informationaccording to an aspect of the present invention, link state informationwhich should be distributed through multiple TE LSAs heretofore can thenbe distributed through only one TE LSA so that the number of TE linksused to distribute link state information can be decreasedsignificantly, traffic flooded in the network is decreased greatly, andnetwork performance is increased.

In the implementation of an aspect of the present invention, dynamicallyadding, modifying or deleting part of multiplex sections can besupported in case that there exists traffic in some multiplex sections.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating the bandwidth resourceprotection state on the link of a two-fiber bidirectional multiplexsection shared protection ring.

FIG. 2 is a schematic diagram illustrating a four-spot-connected networkarchitecture.

DETAILED DESCRIPTION OF THE INVENTION

The core idea of the present invention is carrying the protectionattribute section information in a customized secondary TLV anddistributing the secondary TLV in an optical network, so as to floodvarious protection type information of TE links in an optical networkwith less traffic distribution.

An optical fiber is usually provided with multiple protection types, sothat bandwidth resources of different parts are likely to have differentprotection attributes. Therefore, the protection attribute is no longerthe attribute of the whole TE link and can no longer be represented byNo. 14 secondary TLV.

Referring to FIG. 1, the protection states of bandwidth resources on thelink of a two-fiber bidirectional multiplex section shared protectionring are: protected bandwidth resource for channels 1˜3 and channel 8,protecting bandwidth resource for channels 9˜11 and channel 16 (it isassumed the minimum bandwidth granularity is VC4), and unprotectedbandwidth resource for the rest channels. The bandwidth resource of theTE link is divided into several parts. Therefore, in an embodiment ofthe present invention, bandwidth resources with different protectionattributes on a TE link are represented by section structure, and theprotection attributes are transferred into each protection attributesection structure, and one TE link can have multiple section structures.

In order to better understand the present invention, hereinafter anembodiment of the present invention will be described in detail withreference to the attached drawings.

In the embodiment of the present invention, all link state informationon TE links is placed in TE link TLVs to be flooded, wherein theinformation such as link type, link ID, local interface IP address,remote interface IP address, Unreserved bandwidth, Shared Risk LinkGroup and Interface Switching Capability Descriptor (link protectiontype is not included), etc, is located in a standard defined secondaryTLV, and private information is placed in a customized secondary TLV.

The core of the method according to an embodiment of the presentinvention is adding two fields in the customized secondary TLV:

field for the number of link protection attribute section structures andfield for the offset of link protection attribute section structures,wherein:

the field for the number of link protection attribute section structuresis used to carry the number of link protection attribute sectionstructures; the number of link protection attribute section structuresis the number of different protection types in a whole TE link.Referring to FIG. 1, the number of link protection attribute sectionstructures is 3.

The field for the offset of link protection attribute section structuresis used to carry an offset of link protection attribute sectionstructures; the offset of link protection attribute section structuresis an offset from the TLV header to the link protection attributesection structure sequence; the protection attribute section structuresequence carries information of each link protection attribute section,such as protection type, section bandwidth resource, etc; theintroduction of the design of offset pointer structure can facilitaterepresentation of uncertain length sections.

An embodiment of the present invention utilizes the above extensionfield to carry the protection attribute information of the bandwidthresource with different protection types included in an optical fiber,so as to carry all the protection attribute information in the opticalfiber in a secondary TLV and flood it in the network via TE LSA,achieving effective distribution of the link state information of TElinks in the whole network.

Hereinafter the content information carried in the field of linkprotection attribute section structure in the present invention will bedescribed in detail with reference to the attached drawings.

In an embodiment of the present invention, the link protection attributesection information in the field of each link protection attributesection structure includes: protection type of the section, bandwidthresource occupied by the section, etc; hereinafter the two kinds ofsection information will be described.

In the field of link protection attribute section structure, theprotection types include: Extra Traffic, Unprotected, Shared, Dedicated1:1, Dedicated 1+1 or Enhanced, etc. The traffic on the protectedbandwidth resource is protected, as to two-fiber multiplex sectionprotection ring, the protection type is “Shared”; as to 4-fiber MS-SPR,the protection type is “Enhanced”. The protection attribute forunprotected bandwidth resource is “Unprotected”. Protecting bandwidthresource can be used to carry extra traffic, so the protection attributeis “Extra Traffic”. Referring to FIG. 1, channels 1˜3 and channel 8 areprotected bandwidth resources, so the corresponding protection attributein protection attribute section structure is “Shared”; correspondingly,channels 9˜11 and channel 8 are protecting bandwidth resources, so thecorresponding protection attribute in protection attribute sectionstructure is “Extra Traffic”; the protection attribute in protectionattribute section structure for the rest channels of non-protectedbandwidth resource is “Unprotected”.

In the protection attribute section structure, the representation of thebandwidth resource includes two fields: the minimum bandwidth supportedby the section (i.e., the minimum bandwidth granularity) and thebandwidth resource occupied by the section.

In order to make it to be understood clearly, the content information ofeach field in the protection attribute section structure according to anembodiment of the present invention will be described with reference toa specific example.

Referring to FIG. 1, part of the sections in the customized TLV is shownin Table 1.

TABLE 1 TIV_type QODM_LINK_TLV_TE_PARAMS TIV_length Length of the TLV,the value is filled up as needed . . . . . . The number of link 3protection attribute sections Header offset of link Offset from thestart of the TLV to the protection attribute section protectionattribute section structure

Table 2 shows the fields of the protection attribute section structurein the customized TLV.

TABLE 2 Protection type of the first section Shared Minimum bandwidth ofthe first section 155.520M Bandwidth resource occupied by the firstsection 622.080M Protection type of the second section Extra Minimumbandwidth of the second section 155.520M Bandwidth resource occupied bythe second section 622.080M Protection type of the third sectionUnprotected Minimum bandwidth of the third section 155.520M Bandwidthresource occupied by the third section 1244.160M 

The method according to an embodiment of the present invention can bealso used to distribute link state information in span protection;referring to FIG. 2, in a four-spot-connected MESH network, it isassumed that signals transmitted by optical fiber between two networkelements is STM-64, i.e., the bandwidth resources are 64 VC4s.

With span protection, if 42 VC4s thereof are configured as workingchannels, 21 VC4s are used as protecting channels (used to protect otherlinks), and the rest one is a non-protected channel. In this case, ifthe optical fiber between A and B is disconnected, the traffic on the 42VC4s thereof will go through the other two paths, wherein 21 VC4s gothrough the protecting channels of ACB, and the other 21 VC4s go throughthe protecting channels of ADB. It can be seen that in span protection,various protection types, rather than one, can be provided for oneoptical fiber. Therefore, for span protection, the object of the presentinvention can be also achieved by describing the protection attributeinformation using the protection attribute section structures accordingto an embodiment of the present invention, i.e., various protectiontypes are provided for one TE link can include and the link stateinformation on the TE link can be flooded in the network by less floodedtraffic.

The above-mentioned embodiments of the present invention are preferable.The protective scope of the present invention is not limited to theseembodiments. Any variation or substitution within the technical scope ofthe present invention, which can be easily worked out by those skilledin the art, should be fallen in the protective scope of the presentinvention as defined in the attached claims.

1. A method for implementing distribution of link state information inan optical network, comprising the steps of: determining information ofeach link protection attribute section included in a Traffic Engineering(TE) link; carrying the information of each link protection attributesection included in the TE link in a customized Type Length Value (TLV),respectively, the customized TLV comprising a field for a number of linkprotection attribute section structures, wherein the number of linkprotection attribute section structures is the number of differentprotection types in the TE link; distributing the customized TLV in theoptical network via Traffic Engineering Link State Advertisement (TELSA).
 2. The method for implementing distribution of link stateinformation in an optical network according to claim 1, wherein the stepof determining information of each link protection attribute sectionincluded in a TE link further includes the step of: determining thenumber of link protection attribute section structures for the TE Linkand information of each link protection attribute section carried ineach link protection attribute section structure, in accordance with asubscriber configuration on the TE link.
 3. The method for implementingdistribution of link state information in an optical network accordingto claim 2, wherein the step of carrying the information of each linkprotection attribute section included in the TE link in a customizedType Length Value (TLV) respectively further includes the step of:carrying the information of each link protection attribute section onthe TE link in a field of link protection attribute section structure ofthe customized TLV.
 4. The method for implementing distribution of linkstate information in an optical network according to claim 1, whereinthe information of each link protection attribute section comprises:protection type of the link protection attribute section and/orinformation of a bandwidth resource occupied by the link protectionattribute section.
 5. The method for implementing distribution of linkstate information in an optical network according to claim 4, whereinthe step of carrying the information of each link protection attributesection included in the TE link in a customized Type Length Value (TLV)respectively further includes the step of: carrying the information ofeach link protection attribute section on the TE link in a field of linkprotection attribute section structure of the customized TLV.
 6. Themethod for implementing distribution of link state information in anoptical network according to claim 1, wherein the step of carrying theinformation of each link protection attribute section included in the TElink in a customized Type Length Value (TLV) respectively furtherincludes the step of: carrying the information of each link protectionattribute section on the TE link in a field of link protection attributesection structure of the customized TLV.
 7. A method for implementingdistribution of link state information in an optical network, comprisingthe steps of: determining information of each link protection attributesection included in a Traffic Engineering (TE) link; carrying theinformation of each link protection attribute section included in the TElink in a field of link protection structure of a customized Type LengthValue (TLV), respectively; distributing the customized TLV in theoptical network via Traffic Engineering Link State Advertisement (TELSA); wherein the customized TLV further comprises: a field for thenumber of link protection attribute section structures, wherein thenumber of link protection attribute section structures is the number ofdifferent protection types in the TE link, which is used to carry thenumber of the link protection attribute section structures divided froma bandwidth resource in accordance with a subscriber configuration onthe TE link; a field for an offset of link protection attribute sectionstructures, which is used to carry an offset from the start of thecustomized TLV to the information of each link protection attributesection; wherein an offset pointer points to a link protection attributesection structure sequence which is used to carry the information ofeach link protection attribute section.
 8. The method for implementingdistribution of link state information in an optical network accordingto claim 7, wherein a protection type for each link protection attributesection include: Extra, Unprotected, Shared, Dedicated 1:1, Dedicated1+1 and Enhanced.
 9. The method for implementing distribution of linkstate information in an optical network according to claim 8, whereininformation for the bandwidth resource occupied by a particular linkprotection attribute section comprises: a minimum bandwidth supported bythe particular link protection attribute section and the bandwidthresource occupied by the particular link protection attribute section.